We seek to understand a molecular basis for water transport by solving the crystal structure of CHIP28. It functions as a diffusion-limited passive pore that dissipates osmotic gradients across cell membranes. By sequence homology, CHIP28 has been shown to be a member of a family of channel/transport proteins. We propose to determine an ab initio molecular envelope with a new approach developed that requires the measurement of all of the low-resolution reflections.